In a wet solar cell, a photoresponsive electrode which is an electrode for responding to light and a counter electrode are fixed in an electrolyte and by irradiating the photoresponsive electrode with light, a photoelectric current is generated between the photoresponsive electrode and the counter electrode to obtain an electromotive force.
Such a wet solar cell has been vigorously investigated as a solar cell capable of obtaining a high photoelectric transformation efficiency and, in particularly, a wet solar cell using a photoresponsive electrode formed by fixing various organic molecules onto the surface of a metal is expected to be able to attain a very high photoelectric transformation efficiency by designing high-performance photoresponsive molecules and by controlling the orientation of the molecules, and thus the investigation and development of the wet solar cell have been vigorously made.
However, because in a conventional wet solar cell, such a photoresponsive electrode is directly irradiated with light, a major part of the incident light is reflected at the metal surface of the photoresponsive electrode and only a part of the irradiated light excites the photoresponsive molecule on the surface of the metal to generate a photoelectric current, which becomes a factor of preventing the remarkable improvement of the photoelectric transformation efficiency.
Also, the sunlight has a broad spectrum of from ultraviolet to infrared, and in these wavelengths of the sunlight, the wavelengths of the highest average radiation intensity on the surface of the earth are the wavelengths of a red light of about 700 nm. However, a conventional photoresponsive electrode mainly responds to the light of from purple to green having wavelengths of from about 400 to 500 nm and thus by a red light having a low energy, the exciting efficiency of the photoresponsive electrode is greatly lowered, which causes the problem that the amount of the electric power generated by the low energy light is lowered to reduce the electric power generation and the stability of the solar cell using the conventional photoresponsive electrode.